What Pyrocumulus Clouds are and how they are Formed

Pyrocumulus clouds are dense cumulus clouds which form due to surface heating. Pyrocumulus clouds are created by fire either from a volcanic eruption or a wildfire. These clouds are usually found anywhere between 2,000 to 30,000 feet above the ground, and they’re created by the ashes of volcanic eruptions and fire, as well as water vapor.  Pyrocumulus clouds can produce rain and extinguish the fire that created it or produce lightning and start another fire. The following summarizes what pyroculus clouds are and how they are formed.

Pyrocumulus clouds take their name from the Latin word Pyro which means “fire” and the word cumulus which means “pile up.” Literally, pyrocumulus means fire cloud. Natural or man-made fires can add sufficient heat into the atmosphere to warm the air near the surface of the ground, resulting in the formation of a pyrocumulus cloud.

A pyrocumulus cloud forms as a result of intense heat in the surface of the ground and subsequent transfer of heat by convection, causing an air mass to rise up in the atmosphere. A fire can produce vigorous lifting air currents along with huge amounts of water vapor and ash particles released from the combustion of vegetation. Ash particles serve as nuclei around which rising water vapor will condense (reaching dew point), forming a pyrocumulus cloud. 

Natural phenomena, including forest fires and volcanic eruptions can induce the formation of pyrocumulus clouds; however, nuclear weapon detonations and industrial activities may produce such a cloud too. The base of a pyrocumulus cloud is obscure due to the amounts of smoke coming from a volcanic eruption or fire, al though the top of the cloud is visible over the smokescreen. Pyrocumulus clouds can form from between 2,000 and 30,000 feet.

Pyrocumulus clouds can produce severe turbulence, which results in strong gusts of air at the surface level which may intensify a large fire.  Occasionally, pyrocumulus moisture content can fall as precipitation or develop into a storm, extinguishing the same fire that created it.  A pyrocumulus cloud can develop into a cumulonimbus (towering vertical cloud) which may produce lightning and start another fire, especially in subtropical latitudes where the abundance of moisture promotes the condensation of warm air.

Pyrocumulus clouds acquire a grayish or brown color due to the ashes and smoke derived from the smoke of a fire.  These types of clouds also tend to spread out due to the great amounts of ashes involved in their formation.  The increased condensation nuclei can trigger a thunderstorm with the added hazard of starting another fire. Pyrocumulus clouds are very common in places where high incidences of fire are not rare.